Materials Characterization

Stable Nanopores in Graphene

June 02, 2014

Z-contrast image of a graphene nanopore passivated with 17 Si atoms.

The existence of stable holes in graphene has been demonstrated. This is a major step toward the development of robust and reliable graphene-based nanopore devices that could be used, for example, in DNA sequencing.

Graphene is the ultimate ultrathin, impervious membrane. However, the introduction of nanopores in graphene would open the possibility of a wide range of applications including water purification, gas separation and molecular translocation. Fabrication of nanopores in graphene have been reported, but there has been no evidence that the created pores were actually formed in single layers and no direct evidence of stable pores with diameters less than 5nm. In fact, it has been shown that small holes in graphene are unstable against filling by adatoms (especially carbon atoms). Using aberration-corrected scanning transmission electron microscopy and density-functional calculations, it was discovered that Si atoms stabilize graphene nanopores by bridging the dangling bonds around the perimeter of the hole. These Si-passivated pores remain open, demonstrating that these structures are intrinsically robust and stable against carbon filling. Theoretical calculations reveal the underlying mechanism for this stabilization effect is that Si atoms bond strongly to the graphene edge, and their preference for tetrahedral coordination forces carbon adatoms to form dendrites sticking out of the graphene plane, instead of filling the nanopore.